Diaryl ether cycloalkanes

ABSTRACT

The invention concerns a diaryl ether cycloalkane of the formula I, or a pharmaceutically-acceptable salt thereof, ##STR1## wherein Ar 1  is optionally substituted phenyl or naphthyl; X 1  is oxy, thio, sulphinyl or sulphonyl; 
     Ar 2  is optionally substituted phenylene, or a 6-membered heterocyclene moiety containing up to three nitrogen atoms; 
     R 1  is (1-6C)alkyl, (3-6C)alkenyl, (3-6C)alkynyl, cyano-(1-4C)alkyl or (2-4C)alkanoyl, or optionally substituted benzoyl; and 
     R 2  and R 3  together form a (3-6C)alkylene group which defines an optionally substituted ring having 4 to 7 ring atoms. 
     The invention also concerns processes for the manufacture of a diaryl ether cycloalkane of the formula I, or a pharmaceutically-acceptable salt thereof, and pharmaceutical compositions containing said cycloalkane. The compounds of the invention are inhibitors of the enzyme 5-lipoxygenase.

This is a continuation of application Ser. No. 07/547,183, filed on Jul. 3, 1990, which is now abandoned.

This invention concerns novel diaryl ether cycloalkanes and more particularly novel diaryl ether cycloalkanes which are inhibitors of the enzyme 5-lipoxygenase (hereinafter referred to as 5-LO). The invention also concerns processes for the manufacture of said diaryl ether cycloalkanes and novel pharmaceutical compositions containing them. Also included in the invention is the use of said diaryl ether cycloalkanes in the treatment of various inflammatory and/or allergic diseases in which the direct or indirect products of 5-LO catalysed oxidation of arachidonic acid are involved, and the production of new medicaments for such use.

As stated above the diaryl ether cycloalkanes described hereinafter are inhibitors of 5-LO, which enzyme is known to be involved in catalysing the oxidation of arachidonic acid to give rise via a cascade process to the physiologically active leukotrienes such as leukotriene B₄ (LTB₄) and the peptido-lipid leukotrienes such as leukotriene C₄ (LTC₄) and leukotriene D₄ (LTD₄) and various metabolites.

The biosynthetic relationship and physiological properties of the leukotrienes are summarised by G. W. Taylor and S. R. Clarke in Trends in Pharmacological Sciences, 1986, 7, 100-103. The leukotrienes and their metabolites have been implicated in the production and development of various inflammatory and allergic diseases such as arthritic diseases, asthma, allergic rhinitis, atopic dermatitis, psoriasis, cardiovascular and cerebrovascular disorders and inflammatory bowel disease. In addition the leukotrienes are mediators of inflammatory diseases by virtue of their ability to modulate lymphocyte and leukocyte function. Other physiologically active metabolites of arachidonic acid, such as the prostaglandins and thromboxanes, arise via the action of the enzyme cyclooxygenase on arachidonic acid.

We have now discovered that certain diaryl ether cycloalkanes are effective as inhibitors of the enzyme 5-LO and thus of leukotriene biosyntheses. Thus, such compounds are of value as therapeutic agents in the treatment of, for example, allergic conditions, psoriasis, asthma, cardiovascular and cerebrovascular disorders, and/or inflammatory and arthritic conditions, mediated alone or in part by one or more leukotrienes.

According to the invention there is provided a diaryl ether cycloalkane of the formula I (set out hereinafter) wherein Ar¹ is phenyl or naphthyl which may optionally bear one or more substituents selected from amino, halogeno, hydroxy, cyano, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkysulphinyl, (1-4C)alkylsulphonyl, (1-4C)alkylamino, di-[(1-4C)alkyl]amino, (1-4C)alkoxycarbonyl, (2-4C)alkanoyl, hydroxy-(1-4C)alkyl, fluoro-(1-4C)alkyl, cyano-(1-4C)alkyl, fluoro-(1-4C)alkoxy, cyano-(1-4C)alkoxy, phenyl and benzoyl, and wherein said phenyl or benzoyl substituent may optionally bear a substituent selected from halogeno, (1-4C)alkyl and (1-4C)alkoxy;

wherein X¹ is oxy, thio, sulphinyl or sulphonyl;

wherein Ar² is phenylene which may optionally bear one or two substituents selected from halogeno, hydroxy, amino, nitro, cyano, carbamoyl, (1-4C)alkyl, (3-4C)alkenyloxy, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl, (1-4C)alkylamino, di-[(1-4C)alkyl]amino, fluoro-(1-4C)alkyl, cyano-(1-4C)alkyl, (1-4C)alkoxycarbonyl, N-[(1-4C)alkyl]carbamoyl, N,N-di-[(1-4C)alkyl]carbamoyl, (2-4C)alkanoylamino, fluoro-(1-4C)alkoxy, cyano-(1-4C)alkoxy, carbamoyl-(1-4C)alkoxy, amino-(2-4C)alkoxy, (1-4C)alkylamino-(2-4C)alkoxy, di-[(1-4C)alkyl]amino-(2-4C)alkoxy and (1-4C)alkoxycarbonyl-(1-4C)alkoxy; or

Ar² is a 6-membered heterocyclene moiety containing up to three nitrogen atoms which may optionally bear one or two substituents selected from halogeno, hydroxy, amino, cyano, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylamino and di-[(1-4C)alkyl]amino;

wherein R¹ is (1-6C)alkyl, (3-6C)alkenyl, (3-6C)alkynyl, cyano-(1-4C)alkyl or (2-4C)alkanoyl, or R¹ is benzoyl which may optionally bear a substituent selected from halogeno, (1-4C)alkyl and (1-4C)alkoxy; and

wherein R² and R³ together form a (3-6C)alkylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 4 to 7 ring atoms, and which ring may bear one or two substituents, which may be the same or different, selected from halogeno, hydroxy, cyano, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl and fluoro-(1-4C)alkyl, or which ring may bear a (1-4C)alkylenedioxy substituent;

or a pharmaceutically-acceptable salt thereof.

The chemical formulae referred to herein by Roman numerals are set out for convenience on a separate sheet hereinafter.

In this specification the generic term "alkyl" includes both straight-chain and branched-chain alkyl groups. However references to individual alkyl groups such as "propyl" are specific for the straight-chain version only and references to individual branched-chain alkyl groups such as "isopropyl" are specific for the branched-chain version only. An analogous convention applies to other generic terms. It is to be understood that, insofar as certain of the compounds of formula I defined above may exist in optically active or racemic forms by virtue of one or more substituents containing an asymmetric carbon atom, the invention includes in its definition of active ingredient any such optically active or racemic form which possesses the property of inhibiting 5-LO. The synthesis of optically active forms may be carried out by standard techniques of organic chemistry well known in the art, for example by synthesis from optically active starting materials or by resolution of a racemic form. Similarly, inhibitory properties against 5-LO may be evaluated using the standard laboratory techniques referred to hereinafter.

Suitable values for the generic terms referred to above include those set out below.

A suitable value for a halogeno substituent which may be present on Ar¹, Ar² or R¹, or on a phenyl or benzoyl substituent on Ar¹, is, for example, fluoro, chloro, bromo or iodo.

A suitable value for a (1-4C)alkyl substituent which may be present on Ar¹, Ar² or R¹, or on a phenyl or benzoyl substituent on Ar¹, is, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl or tert-butyl.

A suitable value for a (2-4C)alkenyl substituent on Ar¹ is, for example, vinyl, allyl, 2-butenyl or 3-butenyl.

A suitable value for a (2-4C)alkynyl substituent on Ar¹ is, for example, ethynyl, 1-propynyl, 2-propynyl, 1-butynyl or 2-butynyl.

A suitable value for a (1-4C)alkoxy substituent which may be present on Ar¹, Ar² or R¹, or on a phenyl or benzoyl substituent on Ar¹, is, for example, methoxy, ethoxy, propoxy, isopropoxy or butoxy.

Suitable values for substituents which may be present on Ar¹ or Ar² include, for example

    ______________________________________                                         for (1-4C)alkythio:                                                                           methylthio, ethylthio, propylthio,                                             isopropylthio and butylthio;                                    for (1-4C)alkylsulphinyl:                                                                     methylsulphinyl, ethylsulphinyl,                                               propylsulphinyl, isopropyl-                                                    sulphinyl and butylsulphinyl;                                   for (1-4C)alkylsulphonyl:                                                                     methylsulphonyl, ethylsulphonyl,                                               propylsulphonyl, isopropylsulphonyl                                            and butylsulphonyl.                                             ______________________________________                                    

A suitable value for a (2-4C)alkanoyl substituent which may be present on Ar¹ or for R¹ when it is (2-4C)alkanoyl is, for example, acetyl, propionyl or butyryl.

Suitable values for substituents which may be present on Ar¹ or Ar² include, for example

    ______________________________________                                         for (1-4C)alkylamino:                                                                         methylamino, ethylamino, propyl-                                               amino and butylamino;                                           for di-[(1-4C)alkyl]amino:                                                                    dimethylamino, diethylamino and                                                dipropylamino;                                                  for (1-4C)alkoxycarbonyl:                                                                     methoxycarbonyl, ethoxycarbonyl and                                            tert-butoxycarbonyl;                                            for fluoro-(1-4C)alkyl:                                                                       fluoromethyl, difluoromethyl,                                                  trifluoromethyl, 2-fluoroethyl, 2,2,2-                                         trifluoroethyl and pentafluoroethyl;                            for cyano-(1-4C)alkyl:                                                                        cyanomethyl, 1-cyanoethyl, 2-                                                  cyanoethyl, 3-cyanopropyl and 2-                                               cyanoprop-2-yl;                                                 for cyano-(1-4C)alkoxy:                                                                       cyanomethoxy, 2-cyanoethoxy and 3-                                             cyanopropoxy;                                                   for fluoro-(1-4C)alkoxy:                                                                      trifluoromethoxy, 2,2,2-trifluoro-                                             ethoxy and pentafluoroethoxy.                                   ______________________________________                                    

A suitable value for a hydroxy-(1-4C)alkyl substituent which may be present on Ar¹ is, for example, hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl, 1-hydroxypropyl, 2-hydroxypropyl or 3-hydroxypropyl.

A suitable value for the number of substituents which may be present on Ar¹ is, for example, one, two or three.

A suitable value for Ar² when it is phenylene is, for example, 1,3-phenylene or 1,4-phenylene.

A suitable value for Ar² when it is a 6-membered heterocyclene moiety containing up to three nitrogen atoms is, for example, pyridylene, pyrimidinylene, pyridazinylene, pyrazinylene or 1,3,5-triazinylene. Conveniently Ar² when it is a 6-membered heterocyclene moiety containing up to three nitrogen atoms is, for example, 2,4-, 2,5-, 3,5- or 2,6-pyridylene, 2,4-, 2,5- or 4,6-pyrimidinylene, 3,5- or 3,6-pyridazinylene or 2,5- or 2,6-pyrazinylene.

Suitable values for substituents which may be present on Ar² include, for example

    ______________________________________                                         for (3-4C)alkenyloxy:                                                                          allyloxy, methylallyloxy, but-2-                                               enyloxy and but-3-enyloxy;                                     for N-[(1-4C)alkyl]-                                                                           N-methylcarbamoyl, N-ethyl-                                    carbamoyl:      carbamoyl and N-propylcarbamoyl;                               for N,N-di-[(1-4C)alkyl]-                                                                      N,N-dimethylcarbamoyl and N,N-                                 carbamoyl:      diethylcarbamoyl;                                              for (2-4C)alkanoylamino:                                                                       acetamido, propionamido and                                                    butyramido;                                                    for carbamoyl-(1-4C)alkoxy:                                                                    carbamoylmethoxy, 2-carbamoyl-                                                 ethoxy and 3-carbamoylpropoxy;                                 for amino-(2-4C)alkoxy:                                                                        2-aminoethoxy, 3-aminopropoxy and                                              4-aminobutoxy;                                                 for (1-4C)alkylamino-                                                                          2-methylaminoethoxy, 3-                                        (2-4C)alkoxy:   methylaminopropoxy and 2-                                                      ethylaminoethoxy;                                              for di-[(1-4C)alkyl]amino-                                                                     2-dimethylaminoethoxy, 3-                                      (2-4C)alkoxy:   dimethylaminopropoxy and 2-                                                    diethylaminoethoxy;                                            for (1-4C)alkoxycarbonyl-                                                                      methoxycarbonylmethoxy, 2-                                     (1-4C)alkoxy:   methoxycarbonylethoxy, ethoxy-                                                 carbonylmethoxy and 2-ethoxy-                                                  carbonylethoxy.                                                ______________________________________                                    

A suitable value for R¹ when it is (1-6C)alkyl is, for example, methyl, ethyl, propyl, butyl, pentyl or hexyl.

A suitable value for R¹ when it is (3-6C)alkenyl is, for example, allyl, 2-butenyl or 3-butenyl; and when it is (3-6C)alkynyl is, for example 2-propynyl or 2-butynyl.

A suitable value for R¹ when it is cyano-(1-4C)alkyl is, for example, cyanomethyl, 2-cyanoethyl or 3-cyanopropyl.

A suitable value for R² and R³ when they together form a (3-6C)alkylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 4 to 7 ring atoms is, for example, trimethylene, tetramethylene, pentamethylene or hexamethylene. Suitable values for the one or two substituents which may be present on said 4- to 7-membered ring include for example:

    ______________________________________                                         for halogeno:  fluoro, chloro and bromo;                                       for (1-4C)alkyl:                                                                              methyl, ethyl, propyl, isopropyl                                               and butyl;                                                      for (1-4C)alkoxy:                                                                             methoxy, ethoxy, propoxy, isopropoxy                                           and butoxy;                                                     for (1-4C)alkythio:                                                                           methylthio, ethylthio, propylthio,                                             isopropylthio and butylthio;                                    for (1-4C)alkylsulphinyl:                                                                     methylsulphinyl, ethylsulphinyl,                                               propylsulphinyl, isopropyl-                                                    sulphinyl and butylsulphinyl;                                   for (1-4C)alkylsulphonyl:                                                                     methylsulphonyl, ethylsulphonyl,                                               propylsulphonyl, isopropylsulphonyl                                            and butylsulphonyl;                                             for fluoro-(1-4C)alkyl:                                                                       fluoromethyl, difluoromethyl,                                                  trifluoromethyl, 2-fluoroethyl,                                                2,2,2-trifluoroethyl and penta-                                                fluoroethyl;                                                    for (1-4C)alkylenedioxy:                                                                      methylenedioxy and ethylenedioxy.                               ______________________________________                                    

A suitable pharmaceutically-acceptable salt of a diaryl ether cycloalkane of the invention is, for example, an acid-addition salt of a diaryl ether cycloalkane of the invention which is sufficiently basic, for example, an acid-addition salt with, for example, an inorganic or organic acid, for example hydrochloric, hydrobromic, sulphuric, phosphoric, trifluoroacetic, citric or maleic acid. In addition a suitable pharmaceutically-acceptable salt of a diaryl ether cycloalkane of the invention which is sufficiently acidic is an alkali metal salt, for example a sodium or potassium salt, an alkaline earth metal salt, for example a calcium or magnesium salt, an ammonium salt or a salt with an organic base which affords a physiologically-acceptable cation, for example a salt with methylamine, dimethylamine, trimethylamine, piperidine, morpholine or tris-(2-hydroxyethyl)amine.

Particular novel compounds of the invention are, for example, diaryl ether cycloalkanes of the formula I wherein:

(a) Ar¹ is phenyl, naphth-1-yl or naphth-2-yl which may optionally bear one, two or three substituents selected from amino, fluoro, chloro, bromo, iodo, cyano, methyl, ethyl, isopropyl, tert-butyl, methoxy, methylthio, methylsulphinyl, methylsulphonyl, methoxycarbonyl, difluoromethyl, trifluoromethyl, 1-cyanoethyl, 2-cyanoethyl, 2-cyanoprop-2-yl and cyanomethoxy; and X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore;

(b) Ar¹ is phenyl or naphth-2-yl which may optionally bear one or two substituents selected from fluoro, chloro, methyl, ethyl, isopropyl, tert-butyl, methoxy, trifluoromethyl, 2-cyanoprop-2-yl, phenyl and benzoyl, and wherein said phenyl or benzoyl substituent may optionally bear a substituent selected from chloro, methyl and methoxy; and X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore;

(c) X¹ is thio, sulphinyl or sulphonyl; and Ar¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore;

(d) Ar² is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, chloro, hydroxy, amino, nitro, methyl, methoxy, methylthio, methylsulphinyl, methylsulphonyl, methylamino, dimethylamino, trifluoromethyl, acetamido, cyanomethoxy and carbamoylmethoxy; and Ar¹, X¹, R¹, R² and R³ have any of the meanings defined hereinbefore;

(e) Ar² is 1,3-phenylene which may optionally bear a substituent selected from fluoro, chloro, bromo and trifluoromethyl; and Ar¹, X¹, R¹, R² and R³ have any of the meanings defined hereinbefore;

(f) Ar² is 2,4-, 2,5-, 3,5- or 2,6-pyridylene or 4,6-pyrimidylene which may optionally bear one substituent selected from chloro, methyl and methoxy; and Ar¹, X¹, R¹, R² and R³ have any of the meanings defined hereinbefore;

(g) Ar² is 3,5-pyridylene; and Ar¹, X¹, R¹, R² and R³ have any of the meanings defined hereinbefore;

(h) R¹ is methyl, ethyl, allyl, 2-propynyl or cyanomethyl; and Ar¹, X¹, Ar², R² and R³ have any of the meanings defined hereinbefore;

(i) R¹ is methyl, ethyl, allyl or 2-propynyl; and Ar¹, X¹, Ar², R² and R³ have any of the meanings defined hereinbefore;

(j) R² and R³ together form a tetramethylene or pentamethylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 or 6 ring atoms and which ring may bear one or two substituents, which may be the same or different, selected from fluoro, hydroxy, methyl, methoxy, ethoxy, methylthio, methylsulphinyl, methylsulphonyl, trifluoromethyl and methylenedioxy; and Ar¹, X¹, Ar² and R¹ have any of the meanings defined hereinbefore;

(k) R² and R³ together form a tetramethylene or pentamethylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 or 6 ring atoms and which ring may bear one or two substituents selected from methyl, methoxy and ethoxy; and Ar¹, X¹, Ar² and R¹ have any of the meanings defined hereinbefore; or a pharmaceutically-acceptable salt thereof.

A preferred compound of the invention comprises a diaryl ether cycloalkane of the formula I wherein Ar¹ is phenyl, naphth-1-yl or naphth-2-yl which may optionally bear one or two substituents selected from amino, fluoro, chloro, cyano, methyl, tert-butyl, methoxy, methylthio, methylsulphinyl, methylsulphonyl and 2-cyanoprop-2-yl;

X¹ is thio, sulphinyl or sulphonyl;

Ar² is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, hydroxy, amino, nitro, methoxy, methylamino, cyanomethoxy and trifluoromethyl; or

Ar² is 3,5-pyridylene;

R¹ is methyl or ethyl;

R² and R³ together form a tetramethylene or pentamethylene group, which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 or 6 ring atoms and which ring may bear one or two substituents, which may be the same or different, selected from fluoro, methyl, methoxy and trifluoromethyl;

or a pharmaceutically-acceptable salt thereof.

A further preferred compound of the invention comprises a diaryl ether cycloalkane of the formula I wherein

Ar¹ is phenyl or naphth-2-yl which may optionally bear one or two substituents selected from fluoro, chloro, methyl, ethyl, isopropyl, tert-butyl, methoxy, trifluoromethyl, 2-cyanoprop-2-yl, phenyl and benzoyl, and wherein said phenyl or benzoyl substituent may optionally bear a substituent selected from chloro, methyl and methoxy;

X¹ is oxy, thio, sulphinyl or sulphonyl;

Ar² is 1,3-phenylene which may optionally bear a substituent from fluoro, chloro, bromo and trifluoromethyl; or

Ar² is 3,5-pyridylene;

R¹ is methyl, ethyl, allyl or 2-propynyl;

R² and R³ together form a tetramethylene or pentamethylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 or 6 rings atoms and which ring may bear one or two substituents selected from methyl, methoxy and ethoxy; or a pharmaceutically-acceptable salt thereof.

A further preferred compound of the invention comprises a diaryl ether cycloalkane of the formula I wherein Ar¹ is phenyl which may optionally bear one or two substituents selected from fluoro, chloro, methyl, tert-butyl, methylthio, methylsulphinyl and 2-cyanoprop-2-yl; or

Ar¹ is naphth-2-yl which may optionally bear a fluoro substituent;

X¹ is thio, sulphinyl or sulphonyl;

Ar² is 1,3-phenylene which may optionally bear one substituent selected from fluoro, amino, nitro, methoxy and trifluoromethyl; or

Ar² is 3,5-pyridylene;

R¹ is methyl or ethyl;

R² and R³ together form a tetramethylene or pentamethylene group, which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 or 6 ring atoms and which ring bears a methoxy substituent;

or a pharmaceutically-acceptable salt thereof.

A further preferred compound of the invention comprises a diaryl ether cycloalkane of the formula I wherein

Ar¹ is phenyl which bears a substituent selected from tert-butyl and phenyl; or

Ar¹ is naphth-2-yl;

X¹ is thio, sulphinyl or sulphonyl;

Ar² is 1,3-phenylene wihch are moptonally bear a substituent selected from fluoro, chloro, bromo and trifluoromethyl;

R¹ is methyl, ethyl or allyl;

R² and R³ together from a tetramethylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 ring atoms and which ring bears a methoxy substituent;

or a pharmaceutically-acceptable salt thereof.

Specific especially preferred compounds of the invention include, for example, the following diaryl ether cycloalkanes of the formula I, or pharmaceutically-acceptable salts thereof: (1RS, 2SR)-1-[5-fluoro-3-(naphth-2-ylthio)phenyl]-1,2-dimethoxycyclopentane and (1RS,2SR)-1-allyloxy-1-[5-fluoro-3-(naphth-2-ylthio)-phenyl]-2-methoxycyclopentane.

According to a further aspect the invention there is provided a diaryl ether cycloalkane of the formula I (set out hereinafter) wherein Ar¹ is phenyl or naphthyl which may optionally bear one or more substituents selected from amino, halogeno, hydroxy, cyano, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkysulphinyl, (1-4C)alkylsulphonyl, (1-4C)alkylamino, di-[(1-4C)alkyl]amino, (1-4C)alkoxycarbonyl, (2-4C)alkanoyl, hydroxy-(1-4C)alkyl, fluoro-(1-4C)alkyl, cyano-(1-4C)alkyl, fluoro-(1-4C)alkoxy and cyano-(1-4C)alkoxy;

wherein X¹ is oxy, thio, sulphinyl or sulphonyl;

wherein Ar² is phenylene which may optionally bear one or two substituents selected from halogeno, hydroxy, amino, nitro, cyano, carbamoyl, (1-4C)alkyl, (3-4C)alkenyloxy, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkysulphonyl, (1-4C)alkylamino, di-[(1-4C)alkyl]amino, fluoro-(1-4C)alkyl, cyano-(1-4C)alkyl, (1-4C)alkoxycarbonyl, N-[(1-4C)alkyl]carbamoyl, N,N-di-[(1-4C)alkyl]carbamoyl, (2-4C)alkanoylamino, fluoro-(1-4C)alkoxy, cyano-(1-4C)alkoxy, carbamoyl-(1-4C)alkoxy, amino-(2-4C)alkoxy, (1-4C)alkylamino-(2-4C)alkoxy, di-[(1-4C)alkyl]amino-(2-4C)alkoxy and (1-4C)alkoxycarbonyl-(1-4C)alkoxy; or

Ar² is a 6-membered heterocyclene moiety containing up to three nitrogen atoms which may optionally bear one or two substituents selected from halogeno, hydroxy, amino, cyano, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylamino and di-[(1-4C)alkyl]amino; wherein R¹ is (1-6C)alkyl, (3-6C)alkenyl, (3-6C)alkynyl, cyano-(1-4C)alkyl or (2-4C)alkanoyl, or R¹ is benzoyl which may optionally bear a substituent selected from halogeno, (1-4C)alkyl and (1-4C)alkoxy; and

wherein R² and R³ together form a (3-6C)alkylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 4 to 7 ring atoms, and which ring may bear one or two substituents, which may be the same or different, selected from halogeno, hydroxy, cyano, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl and fluoro-(1-4C)alkyl, or which ring may bear a (1-4C)alkylenedioxy substituent;

or a pharmaceutically-acceptable salt thereof.

A compound of the invention comprising a diaryl ether cycloalkane of the formula I, or a pharmaceutically-acceptable salt thereof, may be prepared by any process known to be applicable to the preparation of structurally-related compounds. Such procedures are provided as a further feature of the invention and are illustrated by the following representative examples in which, unless otherwise stated, Ar¹, X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore.

(a) The coupling, in the presence of a suitable base, of a compound of the formula Ar¹ --X¹ --H with a compound of the formula II wherein Z is a displaceable group; provided that, when there is an amino, alkylamino or hydroxy group in Ar¹, Ar², R² or R³ any amino, alkylamino or hydroxy group may be protected by a conventional protecting group or alternatively any such group need not be protected;

whereafter any undesired protecting group in Ar¹, Ar², R² or R³ is removed by conventional means.

A suitable displaceable group Z is, for example, a halogeno or sulphonyloxy group, for example a chloro, bromo, iodo, methanesulphonyloxy or toluene-p-sulphonyloxy group.

A suitable base for the coupling reaction is, for example, an alkali or alkaline earth metal carbonate, (1-4C)alkoxide, hydroxide or hydride, for example sodium carbonate, potassium carbonate, sodium ethoxide, sodium butoxide, sodium hydroxide, potassium hydroxide, sodium hydride or potassium hydride. The alkylation reaction is preferably performed in a suitable inert solvent or diluent, for example N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, acetone, 1,2-dimethoxyethane or tetrahydrofuran, and at a temperature in the range, for example, 10° to 150° C., conveniently at or near 100° C.

Conveniently the reaction may be performed in the presence of a suitable catalyst, for example a metallic catalyst, for example palladium(O) or copper(I) such as tetrakis(triphenylphosphine)-palladium, cuprous chloride or cuprous bromide.

A suitable protecting group for an amino or alkylamino group is, for example, an acyl group for example a (1-4C)alkanoyl group (especially acetyl), a (1-4C)alkoxycarbonyl group (especially methoxycarbonyl, ethoxycarbonyl or tert-butoxycarbonyl), an arylmethoxycarbonyl group (especially benzyloxycarbonyl) or an aroyl group (especially benzoly). The deprotection conditions for the above protecting groups necessarily vary with the choice of protecting group. Thus, for example, an acyl group such as an alkanoyl or alkoxycarbonyl or an aroyl group may be removed for example, by hydrolysis with a suitable base such as an alkali metal hydroxide, for example lithium or sodium hydroxide. Alternatively an acyl group such as a tert-butoxycarbonyl group may be removed, for example, by treatment with a suitable acid such as hydrochloric, sulphuric or phosphoric acid or trifluoroacetic acid and an arylmethoxycarbonyl group such as a benzyloxycarbonyl group may be removed, for example, by hydrogenation over a catalyst such as palladium-on-charcoal.

A suitable protecting group for a hydroxy group is, for example, an acyl group, for example a (1-4C)alkanoyl group (especially acetyl), an aroyl group (especially benzoyl) or an arylmethyl group (especially benzyl). The deprotection conditions for the above protecting groups will necessarily vary with the choice of protecting group. Thus, for example, an acyl group such as an alkanoyl or an aroyl group may be removed, for example, by hydrolysis with a suitable base such as an alkali metal hydroxide, for example lithium or sodium hydroxide. Alternatively an arylmethyl group such as a benzyl group may be removed, for example, by hydrogenation over a catalyst such as palladium-on-charcoal.

The starting materials of the formula Ar¹ --X¹ --H and of the formula II may be obtained by standard procedures of organic chemistry.

Conveniently intermediates of the formula II wherein Z, Ar², R¹, R² and R³ have the meanings defined hereinbefore, may be obtained by way of compounds of the formula Z--Ar² --Y, wherein Z and Ar² have the meanings defined hereinbefore and Y is, for example, a halogeno, formyl, alkanoyl, nitrile or alkoxycarbonyl group, as illustrated in accompanying Scheme I (set out hereinafter).

It will also be appreciated that the intermediate of the formula II may conveniently be obtained from the compound of the formula Z--Ar² --Y, as defined hereinbefore, by reversing the order of introduction of the groups R² and R³ which is used in Scheme I.

(b) The coupling, in the presence of a suitable base as defined hereinbefore, of a compound of the formula III with a compound of the formula Ar¹ --Z wherein Z is a displaceable group as defined hereinbefore; provided that, when there is an amino, alkylamino or hydroxy group in Ar¹, Ar², R¹, R² or R³, any amino, alkylamino or hydroxy group may be protected by a conventional protecting group as defined hereinbefore or alternatively any such group need not be protected;

whereafter any desired protecting group in Ar¹, Ar², R¹, R² or R³ is removed by conventional means.

The coupling reaction is conveniently performed in a suitable inert solvent as defined hereinbefore and at a temperature in the range, for example, 10° to 200° C., conveniently in the range 70° to 150° C. The reaction may conveniently be performed in the presence of a suitable catalyst as defined hereinbefore.

The starting materials of the formula Ar¹ --Z and of the formula III may be obtained by standard procedures of organic chemistry. Such starting materials are obtainable by analogous procedures to those illustrated in accompanying Scheme II (set out hereinafter) or by modifications thereto which are within the ordinary skill of an organic chemist.

A suitable protecting group R⁴, as employed in Scheme II, is any one of the many such groups known in the art and includes any appropriate protecting group as defined hereinbefore. Examples of such groups are given in Scheme II. The conditions for the introduction and removal of such protecting groups are described in standard textbooks of organic chemistry such as, for example, "Protective Groups in Organic Synthesis" by T W Green (J Wiley and Sons, 1981).

(c) The alkylation, in the presence of a suitable base as defined hereinbefore, of a compound of the formula IV with a compound of the formula R¹ --Z, wherein R¹ and Z have the meanings defined hereinbefore, provided that, when there is an amino, alkylamino or hydroxy group in Ar¹, Ar², R² or R³ any amino, alkylamino or hydroxy group may be protected by a conventional protecting group or alternatively any such group need not be protected; whereafter any undesired protecting group in Ar¹, Ar², R² or R³ is removed by conventional means.

The tertiary alcohol starting material of the formula IV may be obtained by standard procedures of organic chemistry. The preparation of examples of such tertiary alcohols is described within the accompanying non-limiting Examples which are provided for the purpose of illustration only. Further required tertiary alcohol starting materials are obtainable by analogous procedures to those described or by modification thereto which are within the ordinary skill of an organic chemist. Conveniently, and as illustrated in accompanying Scheme III (set out hereinafter), intermediates of the formulae Ar¹ --X¹ --Ar² --Y, wherein Ar¹, X¹ and Ar² have the meanings defined hereinbefore and Y is, for example, a halogeno, formyl, alkanoyl, nitrile or alkoxycarbonyl group may be utilised in the preparation of the tertiary alcohol starting material of the formula IV.

(d) For the production of those compounds of the formula I wherein Ar¹ or Ar² bears an alkylsulphinyl or alkylsulphonyl substituent; wherein X¹ is a sulphinyl or sulphonyl group; or wherein R² and R³ together form a (3-6C)alkylene group which bears one or two alkylsulphinyl or alkylsulphonyl groups; the oxidation of a compound of the formula I wherein Ar¹ or Ar² bears an alkylthio substituent; wherein X¹ is a thio group; or wherein R² and R³ together form a (3-6C)alkylene group which bears one or two alkylthio groups.

A suitable oxidising agent is, for example, any agent known in the art for the oxidation of thio to sulphinyl and/or sulphonyl, for example, hydrogen peroxide, a peracid (such as 3-chloroperoxybenzoic or peroxyacetic acid), an alkali metal peroxysulphate (such as potassium peroxymonosulphate), chromium trioxide or gaseous oxygen in the presence of platinum. The oxidation is generally carried out under as mild conditions as possible and with the required stoichiometric amount of oxidising agent in order to reduce the risk of over oxidation and damage to other functional groups. In general the reaction is carried out in a suitable solvent or diluent such as methylene chloride, chloroform, acetone, tetrahydrofuran or tert-butyl methyl ether and at a temperature, for example, at or near ambient temperature, that is in the range 15° to 35° C. When a compound carrying a sulphinyl group is required a milder oxidising agent may also be used, for example sodium or potassium metaperiodate, conveniently in a polar solvent such as acetic acid or ethanol. It will be appreciated that when a compound of the formula I containing a sulphonyl group is required, it may be obtained by oxidation of the corresponding sulphinyl compound as well as of the corresponding thio compound.

(e) For the production of those compounds of the formula I wherein Ar² bears an alkanoylamino substituent, the acylation of a compound of the formula I wherein Ar² bears an amino substituent.

A suitable acylating agent is, for example, any agent known in the art for the acylation of amino to acylamino, for example an acyl halide, for example a (2-6C)alkanoyl chloride or bromide, in the presence of a suitable base, an alkanoic acid anhydride, for example a (2-6C)alkanoic acid anhydride, or an alkanoic acid mixed anhydride, for example the mixed anhydride formed by the reaction of an alkanoic acid and a (1-4C)alkoxycarbonyl halide, for example a (1-4C)alkoxycarbonyl chloride, in the presence of a suitable base. In general the reaction is carried out in a suitable solvent or diluent such as methylene chloride, acetone, tetrahydrofuran or tert-butyl methyl ether and at a temperature, for example, at or near ambient temperature, that is in range 15° to 35° C. A suitable base when it is required is, for example, pyridine, 4-dimethylaminopyridine, triethylamine, ethyldiisopropylamine, N-methylmorpholine, an alkali metal carbonate, for example potassium carbonate, or an alkali metal carboxylate, for example sodium acetate.

(f) For the production of those compounds of the formula I wherein R¹ is alkanoyl or benzoyl optionally bearing a substituent as defined hereinbefore, the acylation of a compound of the formula I wherein R¹ is hydrogen. For the production of those compounds of the formula I wherein R¹ is alkanoyl the acylation reaction may be carried out using, for example, a suitable acylating agent as defined hereinbefore. For the production of those compounds of the formula I wherein R¹ is benzoyl optionally bearing a substituent the acylation may be carried out using, for example, a benzoyl halide, for example a benzoyl chloride or bromide, in the presence of a suitable base as defined hereinbefore.

When a pharmaceutically-acceptable salt of a novel compound of the formula I is required, it may be obtained, for example, by reaction of said compound with a suitable acid or base using a conventional procedure. When an optically active form of a compound of the formula I is required, it may be obtained by carrying out one of the aforesaid procedures using an optically active starting material, or by resolution of a racemic form of said compound using a conventional procedure.

Many of the intermediates defined herein are novel, for example those of the formulae III and IV and these are provided as a further feature of the invention.

As stated previously, the compounds of the formula I are inhibitors of the enzyme 5-LO. The effects of this inhibition may be demonstrated using one or more of the standard procedures set out below:

a) An in vitro spectrophotometric enzyme assay system, which assesses the inhibitory properties of a test compound in a cell free system using 5-LO isolated from guinea pig neutrophils and as described by D. Aharony and R. L. Stein (J. Biol. Chem., 1986, 261(25), 11512-11519). This test provides a measure of the intrinsic inhibitory properties against soluble 5-LO in an extracellular environment.

b) An in vitro assay system involving incubating a test compound with heparinised human blood, prior to challenge with the calcium ionophore A23187 and then indirectly measuring the inhibitory effects on 5-LO by assaying the amount of LTB₄ using the specific radioimmunoassay described by Carey and Forder (F. Carey and R. A. Forder, Brit. J. Pharmacol. 1985, 84, 34P) which involves the use of a protein-LTB₄ conjugate produced using the procedure of Young et alia (Prostaglandins, 1983, 26(4), 605-613). The effects of a test compound on the enzyme cyclooxygenase (which is involved in the alternative metabolic pathway for arachidonic acid and gives rise to prostaglandins, thromboxanes and related metabolites) may be measured at the same time using the specific radioimmunoassay for thromboxane B₂ (TxB₂) described by Carey and Forder (see above). This test provides an indication of the effects of a test compound against 5-LO and also cyclooxygenase in the presence of blood cells and proteins. It permits the selectivity of the inhibitory effect on 5-LO or cyclooxygenase to be assessed.

c) An ex vivo assay system, which is a variation of test b) above, involving administration of a test compound (usually orally as the suspension produced when a solution of the test compound in dimethylsulphoxide is added to carboxymethylcellulose), blood collection, heparinisation, challenge with A23187 and radioimmunoassay of LTB₄ and TxB₂. This test provides an indication of the bioavailability of a test compound as an inhibitor of 5-LO or cyclooxygenase.

d) An in vitro assay system involving the measurement of the inhibitory properties of a test compound against the liberation of LTC₄ and PGE₂ induced by zymosan on mouse resident peritoneal macrophages, using the procedure of Humes (J. L. Humes et alia, Biochem. Pharmacol., 1983, 32, 2319-2322) and conventional radioimmunoassay systems to measure LTC₄ and PGE₂. This test provides an indication of inhibitory effects against 5-LO and cyclooxygenase in a non-proteinaceous system.

e) An in vivo system involving the measurement of the effects of a test compound in inhibiting the inflammatory response to arachidonic acid in the rabbit skin model developed by D. Aked et alia (Brit. J. Pharmacol., 1986, 89, 431-438). This test provides an in vivo model for 5-LO inhibitors administered topically or orally.

f) An in vivo system involving measuring the effects of a test compound administered orally or intravenously on a leukotriene dependent bronchoconstriction induced by an antigen challenge in guinea pigs pre-dosed with an antihistamine (mepyramine), a β-adrenergic blocking agent (propranolol) and a cyclooxygenase inhibitor (indomethacin), using the procedure of W. H. Anderson et alia (British J. Pharmacology, 1983, 78(1), 67-574). This test provides a further in vivo test for detecting 5-LO inhibitors.

g) An in vivo system involving measuring the effects of a test compound administered orally against the liberation of LTB₄ induced by zymosan within an air pouch generated within the subcutaneous tissue of the back of male rats. The rats are anaesthetised and air pouches are formed by the injection of sterile air (20 ml). A further injection of air (10 ml) is similarly given after 3 days). At 6 days after the initial air injection the test compound is administered (usually orally as the suspension produced when a solution of the test compound in dimethylsulphoxide is added to hydroxypropylmethylcellulose), followed by the intrapouch injection of zymosan (1 ml of a 1% suspension in physiological saline). After 3 hours the rats are killed, the air pouches are lavaged with physiological saline, and the specific radioimmunoassay described above is used to assay LTB₄ in the washings. This test provides an indication of inhibitory effects against 5-LO in an inflammatory milieu.

Although the pharmacological properties of the compounds of the formula I vary with structural changes as expected, in general compounds of the formula I possess 5-LO inhibitory effects at the following concentrations or doses in one or more of the above tests a)-f):

Test a): IC₅₀ in the range, for example, 0.01-30 μM;

Test b): IC₅₀ (LTB₄) in the range, for example, 0.01-40 μM IC₅₀ (TxB₂) in the range, for example, 40-200 μM;

Test c): oral ED₅₀ (LTB₄) in the range, for example, 1-100 mg/kg;

Test d): IC₅₀ (LTC₄) in the range, for example, 0.001-1 μM, IC₅₀ (PGE₂) in the range, for example, 20-1000 μM;

Test e): inhibition of inflammation in the range, for example, 0.3-100 μg intradermally;

Test f): ED₅₀ in the range, for example, 0.5-10 mg/kg i.v.;

Test g): oral ED₅₀ (LTB₄) in the range, for example, 0.5-50 mg/kg.

No overt toxicity or other untoward effects are present in tests c), e), f) and/or g) when compounds of the formula I are administered at several multiples of their minimum inhibitory dose or concentration.

Thus, by way of example, the compound (1RS,2SR)-1-[5-fluoro-3-(naphth-2-ylthio)phenyl]-1,2-dimethoxycyclopentane has an IC₅₀ of approx. 0.2 μM against LTB₄ in test b); and the compound (1RS,2SR)-1-allyloxy-1-[5-fluoro-3-(naphth-2-ylthio)phenyl]-2-methoxycyclopentane also has an IC₅₀ of approx. 0.2 μM against LTB₄ in test b).

These compounds are examples of diaryl ether cycloalkanes of the invention which show selective inhibitory properties for 5-LO as opposed to cyclooxygenase, which selective properties are expected to impart improved therapeutic properties, for example, a reduction in or freedom from the gastrointestinal side-effects frequently associated with cyclooxygenase inhibitors such as indomethacin.

According to a further feature of the invention there is provided a pharmaceutical composition which comprises a diaryl ether cycloalkane of the formula I, or a pharmaceutically-acceptable salt thereof, in association with a pharmaceutically-acceptable diluent or carrier.

The composition may be in a form suitable for oral use, for example a tablet, capsule, aqueous or oily solution, suspension or emulsion; for topical use, for example a cream, ointment, gel or aqueous or oily solution or suspension; for nasal use, for example a snuff, nasal spray or nasal drops; for vaginal or rectal use, for example a suppository; for administration by inhalation, for example as a finely divided powder or a liquid aerosol; for sub-lingual or buccal use, for example a tablet or capsule; or for parenteral use (including intravenous, subcutaneous, intramuscular, intravascular or infusion), for example a sterile aqueous or oily solution or suspension.

In general the above compositions may be prepared in a conventional manner using conventional excipients.

The amount of active ingredient (that is a diaryl ether cycloalkane of the formula I or a pharmaceutically-acceptable salt thereof) that is combined with one or more excipients to produce a single dosage form will necessarily vary depending upon the host treated and the particular route of administration. For example, a formulation intended for oral administration to humans will generally contain, for example, from 0.5 mg to 2 g of active agent compounded with an appropriate and convenient amount of excipients which may vary from about 5 to about 98 percent by weight of the total composition. Dosage unit forms will generally contain about 1 mg to about 500 mg of an active ingredient.

According to a further feature of the invention there is provided a diaryl ether cycloalkane of the formula I, or a pharmaceutically-accetable salt thereof, for use in a method of treatment of the human or animal body by therapy.

The invention also includes a method of treating a disease or medical condition mediated alone or in part by one or more leukotrienes which comprises administering to a warm-blooded animal requiring such treatment an effective amount of an active ingredient as defined above. The invention also provides the use of such an active ingredient in the production of a new medicament for use in a leukotriene mediated disease or medical condition.

The size of the dose for therapeutic or prophylactic purposes of a diaryl ether derivative of the formula I will naturally vary according to the nature and severity of the conditions, the age and sex of the animal or patient and the route of administration, according to well known principles of medicine. As mentioned above, diaryl ether cycloalkanes of the formula I are useful in treating those allergic and inflammatory conditions which are due alone or in part to the effects of the metabolites of arachidonic acid arising by the linear (5-LO catalysed) pathway and in particular the leukotrienes, the production of which is mediated by 5-LO. As previously mentioned, such conditions include, for example, asthmatic conditions, allergic reactions, allergic rhinitis, allergic shock, psoriasis, atopic dermatitis, cardiovascular and cerebrovascular disorders of an inflammatory nature, arthritic and inflammatory joint disease, and inflammatory bowel diseases.

In using a compound of the formula I for therapeutic or prophylactic purposes it will generally be administered so that a daily dose in the range, for example, 0.5 mg to 75 mg per kg body weight is received, given if required in divided doses. In general lower doses will be administered when a parenteral route is employed. Thus, for example, for intravenous administration, a dose in the range, for example, 0.5 mg to 30 mg per kg body weight will generally be used. Similarly, for administration by inhalation, a dose in the range, for example, 0.5 mg to 25 mg per kg body weight will be used.

Although the compounds of the formula I are primarily of value as therapeutic agents for use in warm-blooded animals (including man), they are also useful whenever it is required to inhibit the enzyme 5-LO. Thus, they are useful as pharmacological standards for use in the development of new biological tests and in the search for new pharmacological agents.

By virtue of their effects on leukotriene production, the compounds of the formula I have certain cytoprotective effects, for example they are useful in reducing or suppressing certain of the example they are useful in reducing or suppressing certain of the adverse gastrointestinal effects of the cyclooxygenase inhibitory non-steroidal anti-inflammatory agents (NSAIA), such as indomethacin, acetylsalicylic acid, ibuprofen, sulindac, tolmetin and piroxicam. Furthermore, co-administration of a 5-LO inhibitor of the formula I with a NSAIA can result in a reduction in the quantity of the latter agent needed to produce a therapeutic effect, thereby reducing the likelihood of adverse side-effects. According to a further feature of the invention there is provided a pharmaceutical composition which comprises a diaryl ether cycloalkane of the formula I, or a pharmaceutically-acceptable salt thereof as defined hereinbefore, in conjunction or admixture with a cyclooxygenase inhibitory non-steroidal anti-inflammatory agent (such as mentioned above), and a pharmaceutically-acceptable diluent or carrier.

The cytoprotective effects of the compounds of the formula I may be demonstrated, for example in a standard laboratory model which assesses protection against indomethacin-induced or ethanol-induced ulceration in the gastrointestinal tract of rats.

The compositions of the invention may in addition contain one or more therapeutic or prophylactic agents known to be of value for the disease under treatment. Thus, for example a known platelet aggregation inhibitor, hypolipidemic agent, anti-hypertensive agent, beta-adrenergic blocker or a vasodilator may usefully also be present in a pharmaceutical composition of the invention for use in treating a heart or vascular disease or condition. Similarly, by way of example, an anti-histamine, steroid (such as beclomethasone dipropionate), sodium cromoglycate, phosphodiesterase inhibitor or a beta-adrenergic stimulant may usefully also be present in a pharmaceutical composition of the invention for use in treating a pulmonary disease or condition.

The invention will now be illustrated in the following non-limiting Examples in which, unless otherwise stated:

(i) evaporations were carried out by rotary evaporation in vacuo and work-up procedures were carried out after removal of residual solids by filtration;

(ii) operations were carried out at room temperature, that is in the range 18°-25° and under an atmosphere of an inert gas such as argon;

(iii) column chromatography (by the flash procedure) and medium pressure liquid chromatography (MPLC) were performed on Merck Kieselgel silica (Art. 9385) or Merck Lichroprep RP-18 (Art. 9303) reversed-phase silica obtained from E. Meck, Darmstadt, W. Germany;

(iv) yields are given for illustration only and are not necessarily the maximum attainable;

(v) the end-products of the formula I have satisfactory microanalysis and their structures were confirmed by NMR and mass spectral techniques;

(vi) intermediates were not generally fully characterised and purity was assessed by thin layer chromatographic, infra-red (IR) or NMR analysis;

(vii) melting points are uncorrected and were determined using a Mettler SP62 automatic melting point apparatus or an oil-bath apparatus; melting points for the end-products of the formula I were determined after recrystallisation from a conventional organic solvent such as ethanol, methanol, acetone, ether or hexane, alone or in admixture; and

(viii) the following abbreviations have been used:

    ______________________________________                                         THF             tetrahydrofuran;                                               DMSO            dimethylsulphoxide;                                            DMF             N,N-dimethylformamide;                                         DMA             N,N-dimethylacetamide.                                         ______________________________________                                    

EXAMPLE 1

A mixture of (1RS,2SR)-1-[5-fluoro-3-(naphth-2-ylthio)phenyl]-2-methoxycyclopentanol (0.12 g), sodium hydride (60% w/w dispersion in mineral oil; 0.026 g), 1,4,7,10,13-pentaoxacyclopentadecane (hereinafter 15-crown-5, 0.005 g) and DMF (1.5 ml) was stirred at ambient temperature for 5 minutes. Methyl iodide (0.14 g) was added and the mixture was stirred at ambient temperature for 4 hours. The mixture was partitioned between diethyl ether and water. The organic phase was washed with water and with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using initially petroleum ether (b.p. 40°-60° C.) and then a 1:1 v/v mixture of petroleum ether and methylene chloride as eluent. There was thus obtained (1RS,2SR)-1-[5-fluoro-3-(naphth-2-ylthio)phenyl]-1,2-dimethoxycyclopentane (0.095 g, 76%).

NMR Spectrum (CDCl₃, δ values) 1.5-2.25 (m, 6H), 2.95 (s, 3H), 3.0 (s, 3H), 3.4-3.6 (m, 1H), 6.75-8.0 (m, 10H).

The (1RS,2SR)-1-[5-fluoro-3-(naphth-2-ylthio)phenyl]-2-methoxycyclopentanol used as a starting material was obtained as follows:

Sodium hydride (50% w/w dispersion in mineral oil, 0.58 g) was added portionwise to a mixture of 2-naphthalenethiol (1.6 g) and DMA (15 ml) and the mixture was stirred at ambient temperature for 1.5 hours. 1-Bromo-3,5-difluorobenzene (1.93 g) was added and the mixture was heated to 60° C. for 3 hours. The mixture was allowed to cool to ambient temperature and partitioned between diethyl ether and water. The organic phase was washed with brine (50 ml), dried (MgSO₄) and evaporated. The residue was purified by column chromatography using petroleum ether (b.p. 40°-60° C.) as eluent. There was thus obtained 3-bromo-5-fluorophenyl 2-naphthyl sulphide (2.1 g, 63%) as an oil.

A Grignard reagent was prepared by stirring a mixture of the product so obtained (0.782 g), magnesium powder (0.065 g), THF (1 ml) and a crystal of iodine at ambient temperature for 0.5 hours. A solution of 2-methoxycyclopentanone (0.336 g; Bull. Soc. Chim. France, 1973, 1417) in THF (1 ml) was added and the mixture was stirred at ambient temperature for 15 hours. The mixture was partitioned between diethyl ether and water. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using methylene chloride as eluent. There was thus obtained and separated a mixture of diastereoisomers. The required starting material (0.272 g, 31%) was the more polar diastereoisomer, having the methoxy and hydroxy groups in a trans-relationship.

EXAMPLE 2

The procedure described in Example 1 was repeated except that allyl bromide was used in place of methyl iodide. There was thus obtained (1RS,2SR)-1-allyloxy-1-[5-fluoro-3-(naphth-2-ylthio)phenyl]-2-methoxycyclopentane in 62% yield, as an oil.

NMR Spectrum (CDCl₃, δ values) 1.5-2.25 (m, 6H), 3.0 (s, 3H), 1.25-1.75 (m, 3H), 4.8-5.25 (m, 2H), 5.5-6.0 (m, 1H), 6.75-8.0 (m, 10H).

EXAMPLE 3

The following illustrate representative pharmaceutical dosage forms containing the compound of formula I, or a pharmaceutically-acceptable salt salt thereof (hereafter compound X), for therapeutic or prophylactic use in humans:

    ______________________________________                                         (a) Tablet I               mg/tablet                                               Copound X               100                                                    Lactose Ph. Eur         182.75                                                 Croscarmellose sodium   12.0                                                   Maize starch paste (5% w/v paste)                                                                       2.25                                                  Magnesium stearate       3.0                                               (b) Tablet II              mg/tablet                                               Compound X              50                                                     Lactose Ph. Eur         223.75                                                 Croscarmellose sodium    6.0                                                   Maize starch            15.0                                                   Polyvinylpyrrolidone (5% w/v paste)                                                                     2.25                                                  Magnesium stearate       3.0                                               (c) Tablet III             mg/tablet                                               Compound X               1.0                                                   Lactose Ph. Eur         93.25                                                  Croscarmellose sodium    4.0                                                   Maize starch paste (5% w/v paste)                                                                       0.75                                                  Magnesium stearate       1.0                                               (d) Capsule                mg/capsule                                              Compound X              10 mg                                                  Lactose Ph. Eur         488.5                                                  Magnesium stearate       1.5                                               (e) Injection I            (50 mg/ml)                                              Compound X               5.0% w/v                                              1M Sodium hydroxide solution                                                                           15.0% v/v                                              0.1M Hydrochloric acid                                                         (to adjust pH to 7.6)                                                          Polyethylene glycol 400                                                                                 4.5% w/v                                              Water for injection to 100%                                                (f) Injection II           (10 mg/ml)                                              Compound X               1.0% w/v                                              Sodium phosphate BP      3.6% w/v                                              0.1M Sodium hydroxide solution                                                                         15.0% v/v                                              Water for injection to 100%                                                                           (1 mg/ml,                                           (g) Injection III          buffered to pH 6)                                       Compound X               0.1% w/v                                              Sodium phosphate BP      2.26% w/v                                             Citric acid              0.38% w/v                                             Polyethylene glycol 400                                                                                 3.5% w/v                                              Water for injection to 100%                                                (h) Aerosol I              mg/ml                                                   Compound X              10.0                                                   Sorbitan trioleate      13.5                                                   Trichlorofluoromethane  910.0                                                  Dichlorodifluoromethane                                                                                490.0                                              (i) Aerosol II             mg/ml                                                   Compound X               0.2                                                   Sorbitan trioleate       0.27                                                  Trichlorofluoromethane  70.0                                                   Dichlorodifluoromethane                                                                                280.0                                                  Dichlorotetrafluoroethane                                                                             1094.0                                              (j) Aerosol III            mg/ml                                                   Compound X               2.5                                                   Sorbitan trioleate       3.38                                                  Trichlorofluoromethane  67.5                                                   Dichlorodifluoromethane                                                                               1086.0                                                  Dichlorotetrafluoroethane                                                                              191.6                                              (k) Aerosol IV             mg/ml                                                   Compound X               2.5                                                   Soya lecithin            2.7                                                   Trichlorofluoromethane  67.5                                                   Dichlorodifluoromethane                                                                               1086.0                                                  Dichlorotetrafluoroethane                                                                              191.6                                              ______________________________________                                    

Note

The above formulations may be obtained by conventional procedures well known in the pharmaceutical art. The tablets (a)-(c) may be enteric coated by conventional means, for example to provide a coating of cellulose acetate phthalate. The aerosol formulations (h)-(k) may be used in conjunction with standard, metered dose aerosol dispensers, and the suspending agents sorbitan trioleate and soya lecithin may be replaced by an alternative suspending agent such as sorbitan monooleate, sorbitan sesquioleate, polysorbate 80, polyglycerol oleate or oleic acid. ##STR2## 

What we claim is:
 1. A diaryl ether cycloalkane of the formula Iwherein Ar¹ is phenyl or naphthyl which may optionally bear one or more substituents selected from the group consisting of halogeno, hydroxy, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkysulphinyl, (1-4C)alkylsulphonyl, hydroxy-(1-4C)alkyl, fluoro-(1-4C)alkyl, fluoro-(1-4C)alkoxy, and phenyl, wherein said phenyl substituent may optionally bear a substitutent selected from the group consisting of halogeno, (1-4C)alkyl and (1-4C)alkoxy; wherein X¹ is thio, sulphinyl or sulphonyl; wherein Ar² is phenylene which may optionally bear one or two substituents selected from the group consisting of halogeno, hydroxy, nitro, (1-4C)alkyl, (3-4C)alkenyloxy, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkysulphonyl, fluoro-(1-4C)alkyl, and fluoro-(1-4C)alkoxy; wherein R¹ is (1-6C)alkyl, (3-6C)alkenyl, or (3-6C)alkynyl; and wherein R² and R³ together form a (3-6C)alkylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 4 to 7 ring atoms, and which ring may bear one or two substituents, which may be the same or different, selected from the group consisting of halogeno, hydroxy, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl and fluoro-(1-4C)alkyl,or a pharmaceutically-acceptable salt thereof.
 2. A diaryl ether cycloalkane of the formula I as claimed in claim 1 wherein Ar¹ is phenyl, naphth-1-yl or naphth-2-yl which may optionally bear one or two substituents selected from the group consisting of fluoro, chloro, methyl, tert-butyl, methoxy, methylthio, methylsulphinyl and methylsulphonyl;X¹ is thio, sulphinyl or sulphonyl; Ar² is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from the group consisting of fluoro, hydroxy, nitro, methoxy and trifluoromethyl; R¹ is methyl or ethyl; R² and R³ together form a tetramethylene or pentamethylene group, which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 or 6 ring atoms and which ring may bear one or two substituents, which may be the same or different, selected from the group consisting of fluoro, methyl, methoxy and trifluoromethyl;or a pharmaceutically-acceptable salt thereof.
 3. A diaryl ether cycloalkane of the formula I as claimed in claim 1 whereinAr¹ is phenyl or naphth-2-yl which may optionally bear one or two substituents selected from the group consisting of fluoro, chloro, methyl, ethyl, isopropyl, tert-butyl, methoxy, trifluoromethyl, and phenyl, wherein said phenyl substituent may optionally bear a substituent selected from the group consisting of chloro, methyl and methoxy; X¹ is thio, sulphinyl or sulphonyl; Ar² is 1,3-phenylene which may optionally bear a substituent selected from the group consisting of fluoro, chloro, bromo and trifluoromethyl; R¹ is methyl, ethyl, allyl or 2-propynyl; R² and R³ together form a tetramethylene or pentamethylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 or 6 ring atoms and which ring may bear one or two substituents selected from the group consisting of methyl, methoxy and ethoxy; or a pharmaceutically-acceptable salt thereof.
 4. A diaryl ether cycloalkane of the formula I as claimed in claim 1 wherein Ar¹ is phenyl which may optionally bear one or two substituents selected from the group consisting of fluoro, chloro, methyl, tert-butyl, methylthio and methylsulphinyl; orAr¹ is naphth-2-yl which may optionally bear a fluoro substituent; X¹ is thio, sulphinyl or sulphonyl; Ar² is 1,3-phenylene which may optionally bear one substituent selected from the group consisting of fluoro, nitro, methoxy and trifluoromethyl; R¹ is methyl or ethyl; R² and R³ together form a tetramethylene or pentamethylene group, which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 or 6 ring atoms and which ring bears a methoxy substituent;or a pharmaceutically-acceptable salt thereof.
 5. A diaryl ether cycloalkane of the formula I as claimed in claim 1 whereinAr¹ is phenyl which bears a substituent selected from the group consisting of tert-butyl and phenyl; or Ar¹ is naphth-2-yl; X¹ is thio, sulphinyl or sulphonyl; Ar² is 1,3-phenylene which may optionally bear a substituent selected from the group consisting of fluoro, chloro, bromo and trifluoromethyl; R¹ is methyl, ethyl or allyl; R² and R³ together form a tetramethylene group which, together with the carbon atom to which R² and R³ are attached, defines a ring having 5 ring atoms and which ring bears a methoxy substituent; or a pharmaceutically-acceptable salt thereof.
 6. A diaryl ether cycloalkane of the formula I, as claimed in claim 1 or a pharmaceutically-acceptable salt thereof, selected from the group consisting of (1RS,2SR)-1-[5-fluoro-3-(naphth-2-ylthio)phenyl]-1,2-dimethoxycyclopentane and (1RS,2SR)-1-allkyloxy-1-[5-fluoro-3-(naphth-2-ylthio)phenyl]-2-methoxycyclopentane.
 7. A pharmaceutical composition which comprises a diaryl ether cycloalkane of the formula I, or a pharmaceutically-acceptable salt thereof, as claimed in any one of claims 1 to 6 in a 5-lipoxygenase inhibitory amount in association with a pharmaceutically-acceptable diluent or carrier.
 8. A method of treating an inflammatory or allergic condition in a warm-blooded animal in need of such treatment which comprises administering to said warm-blooded animal a 5-lypoxygenase inhibitory amount of a diaryl ether cycloalkane of the formula I, or a pharmaceutically-acceptable salt thereof, as claimed in any one of claims 1 to
 6. 